THE CRAYFISH AND ITS ALLIES 



115 



Development of Lobsters. Lobsters lay eggs in July and 

 August. In the fall they migrate to deep water, and pass 

 the winter there. In the spring they migrate back to the 

 shore the females tarrying behind the males until the 

 eggs of last summer, which she still carries attached to 

 her swimmerets, shall be further advanced. In June the 

 young hatch out, moult, and swim to the surface. The 



FIG. 111. An early stage of develop- 

 ment of egg. Appendages becom- 

 ing bifid. Paired dotted areas 

 above indicate eyes ; these are fol- 

 lowed by the first three paired ap- 

 pendages : antennules, antennae, 

 and mandibles. Below in the mid- 

 dle line is the forming tail ; above 

 is the mouth. After Herrick. 



FIG. 112. Surface view of egg 

 nauphius. Antennas show begin- 

 ning of segmentation; mandibles 

 and maxillae seen on each side of 

 the abdomen. Embryo 16-18 days 

 old. X 25. From Herrick. 



female now moults, but does not spawn again for a whole 

 year ; that is, she spawns in alternate years. The number 

 of eggs carried varies with the age of the female ; middle- 

 aged lobsters may carry up to one hundred thousand eggs, 

 but the old or young ones as few as three thousand. The 

 egg as freshly laid is about 1.5 millimetres in diameter and 

 is stored with food material, called yolk, much as in the 

 case of the hen's egg. As in the chick, the development 



